ON THE MICRORHEOLOGICAL MODELING OF AGGREGATING COLLOIDS

ABSTRACT

Microrheological modeling of the aggregating colloidal dispersions in frames of the mean-field approach Is used to relate their Theological behavior to the parameters of the aggregates. Three parameters are shown to form a minimum set of values which one should know to elaborate the simplest self-consistent microrheological model of aggregating colloids. They are: the yield strength of the compact structure o, fractal dimension D and the exponent m, which characterizes the dependence of the aggregates radius R vs shear rate S (R ∝ S^−m). Analytic consideration and computer simulations are carried out to determine the exponent m for the aggregates of different type. The behavior of the aggregate depends on the character of the particles Interaction. In general the interaction force can be considered a superposition of central component (equivalent to ordinary spring) and some non-central component. If the non-central Interaction Is relevant, the aggregate internal structure is rigid (I.e. it elastically responds to small deformation), while in the case of purely central Interaction it Is soft (i.e. it Is irreversibly deformed even under the action of lnfinlteslmally small force). The system with purely central particles interaction seems to be a reasonable model for the coagulation in secondary energy minimum, while the system with non-central component represents (at lest qualitatively) the coagulation in primary minimum. The theoretical calculations of the shear viscosity of aggregating